Use `systemctl reload` in logrotate script
In 5f74814 (Use systemctl for sending SIGHUP to the service,
2015-06-29), a direct call to `kill` was replaced with `systemctl kill`.
This can be simplified using `systemctl reload` instead. Doing so also
resolves an issue when `POSIXLY_CORRECT` is set (rhbz#2124488).